Preparation of thermosetting resin



Patented Dec. 14, 1943' PREPARATION OF THERMOSETTING RESIN William R.Collings, Richard D. Freeman, and Richard M. Upright, Midland, Micln,assignors to The Dow Chemical Company, Midland, Mich., a corporation ofMichigan No Drawing. Application August 2, 1940, Serial No. 350,160

11 Claims.

This invention relates to a new acid-resistant thermo-setting resinmaterial, the preparation thereof, and products molded therefrom. Thepresent application is a continuation-inpart of our co-pendingapplication, Serial No.

238,814, filed November 4, 1938, which, in turn, is acontinuation-in-part of applications Serial Nos. 192,500 and 192,501,filed February 2, 1938.

U. S. Patent No. 1,892,409 describes the partial digestion of Wood withan aqueous ammonium phenolate solution at elevated temperatures andpressures, reaction of the digested material with.

formaldehyde, drainage of the liquid from the solid components of thereaction mass, and drying and molding of the latter. We hav found thatthe so-obtained moldings lack strength and are deficient in resistanceto acids and aqueous solutions generally; Further, a long molding timeand the use of extreme pressures is necessary to obtain moldings.

It is, accordingly, an object of th presentinvention to provide a methodof partial digestion or pulping of ligno-cellulosic materials withsolutions of metallic phenolates to form intermediates adapted to beemployed in the production of thermo-setting resins, moldings of whichare strong, hard, and resistant to attack by water, acids, and organicsolvents.

Further objects will become apparent from the following description ofthe invention.

We have discovered that a water-insoluble, filled thermo-setting resinmaterial is formed by (1) pulping a ligno-cellulosic material with a hotaqueous solution comprising as active pulping agents inorganic alkaliand a water-soluble metal salt of a phenol to obtain a dispersion ofcellulose fibers comprising a water-soluble phenolate-lignin complex,(2) reacting an aldehyde with the digestion product to form awatersoluble condensation product, (3) acidifying the resultant mixturto precipitate a thermo-setting resin product on the dispersed cellulosefibers, and (4) separating the solid product so produced. 1

The word pulping as herein employed refers to the breakdown ofligno-cellulosic materials to liberate cellulosic fiber and does notinclude the complete digestion and solution of such materials. Thedegree of digestion involved is generally between 40 and 80 per cent byweight of the lignocellulosic material employed.

According to the invention, th process is carried out by treatingligno-cellulosic material with a solution comprising alkali and awater-soluble phenolate at a temperature between 150 C.,and

the decomposition temperature of the mixture,

preferably between C. and C. The mixture is preferably agitated whileheating under the vapor pressure of the reactants at the temperatureused. When the ligno-cellulosic material is pulped, the reactionmixture, comprising the water-soluble phenolate-lignin complex anddispersed cellulose fibers, is cooled, and an aldehyde added thereto.The reaction mixture is then thoroughly agitated for a period of timeand at a temperature required to cause reaction of the phenolate-lignincomplex with the aldehyde and produce a water-soluble condensationproduct but insufiicient to cause precipitation of the condensationproduct from solution. Following completion of the aldehyde condensationstep, the temperature of the reaction mixture is adjusted to betweenabout 20 and 40 C. and acidified to precipitate thermo-setting resinousmaterial on the cellulose fibers. The filled resin product is separatedby any suitablemeans, for example,

by filtration, and washed with water or dilute aqueous alkali to removesalt and acid residues therefrom. 'I'hemoist resin material is dried attemperatures below 100 C. for a period of time suiiicient to reduce themoisture content thereof to below 8 per cent, but insuificient to causematerial alteration in the fiow characteristics of the product. Thisdried resinintermediate is then adapted for use in the preparation of avariety of molded products.

Various modifications may be made in the procedure described in theforegoing paragraph. For example, the inorganic alkali may beneutralized wholly or in part before the aldehyde is added to thedigestion product. Following the aldehyde condensation step, theacidification of the reaction product may be carried out by pouring suchproduct into an acid solution, in which case the filled resin isobtained in a finely-divided amorphous form. An alternative procedureconsists in adding the acid to the condensation product, whereby theresin is precipitated in the form of spongy aggregates.

In carrying out the foregoing procedure, optimum yields of product areobtained when at least 0.005 pound mol of a water-soluble metal salt ofa phenol is employed for each pound of dry'ligno-cellulosic materialdigested. Amounts of phenolateup to 0.02 pound mol per pound ofligno-cellulosic material or higher may be employed. Variations in theamount of metallic phenolate employed, provided they be within thestated limits, do not materially affect the rate of digestion of theligno-cellulosic material according to the present invention. At leastL005 in the process.

pound mol of inorganic alkali is employed per pound of ligno-celluloseand from 0.01 to 0.02 pound mol of alkali per pound of ligno-celluloseis preferred. Within these limits, the time required for digesting willordinarily be between about 1 and 15 hours. Sufficient water should beused in the treating liquor to keep the alkali concentration above about4 per cent but below about 10 per cent. Further, the ratio of totalweight of liquor used to weight of ligno-cellulosic material digestedshould be within about 5 and 20.

The molding qualities of the filled resins obtained as hereinbeforedescribed depend largely on the conditions of condensation. Resinscapable of being satisfactorily molded under mod erate conditions oftemperature and pressure are obtained when at least 1.25 molarequivalents of aldehyde for each mol of phenolic originally employed isused in the condensation steps. From 2 to 2.5 equivalents of aldehydefor each equivalent of phenoiate has been found to be particularlysatisfactory. Before adding the aldehyde, the free alkali present in thedigestion mixture may be at least partially neutralized to preventlosses through reaction of aldehyde with such alkali. A pH range of from9 to 10 may be employed during the condensation with temperatures at 75to 150 C. A preferred temperature range is between 90 and 115 C., atwhich temperatures the time required for condensation is generally lessthan twohours.

Woods, such as aspen, birch, maple, basswood, poplar,-white pine, andthe like, and such lignocellulosic agricultural products as cornstalks,wheat straw, and dried grasses may be employed Such materials may be inany suitable state of sub-division, e. g., chips, sawdust, finely-groundflour, etc., cured or uncured, oven or air-dried as desired. Ammonium,alkaline earth metal or alkali metal phenolates may be used, c. g.,sodium phenolate, potassium phenolate, barium phenolate, sodiumorthocresolate, barium ortho-cresolate, potassium para-cresolate, sodiumxylenolate, ammonium- 4-chlorophenolate, potassium-chlo-ro-cresolates,and water-soluble metal salts of technical cresylic acid and wooddistillate mixtures. The alkali employed in the digestion liquor ispreferably an alkali metal hydroxide such as sodium hydroxide process,and the like. Acid salts, such as aluminum sulphate, zinc chloride,ammonium sulphate, etc., may be substituted for the free acid.

The thermo-setting and water-insoluble condensation product obtainedaccording to the above-described procedure can be molded to produce aninfusibie resin having desirable properties. If desired, additionalfiller and various modifying agents may be incorporated therewith beforemolding. The filler may be suspended in the liquor after thecondensation step before acidification to supplement the function of thedispersed cellulose fibers, or such filler may be incorporated with thethermo-setting condensation product after precipitation. Among thefillers suitable for use are inert fibrous materials and finely-dividedmineral substances, such as asbestos fiber, wood flour, sawdust, cottonflock, rubber dust, sisal hemp fibers, diatomaceous earth, bentonite,sand, mica, graphite, etc. Other modifying agents include insolublesoaps, plasticizers, natural resins, pigments, dyes, and the like.

While the temperatures and pressures required for molding thethermo-setting material vary with the particular reactants and amountsthereof employed, and the conditions of temperature and pressureprevailing during the reaction, temperatures from to C. and pressuresaround 2000 pounds per square inch have been found satisfactory. Moldingoperations at such.

temperature and pressure have a cycle of 2 to 5 minutes or more,depending on the size of the article fabricated.

The products prepared, as described above, are substantially insolublein both hot and cold alcohol and most other common organic solvents, arenot decomposed or appreciably swelled by prolonged exposure to water oraqueous sulfuric acid, are substantially odorless, bond well with andare non-corrosive to metals, have a high heat resistance, can be exposedto elevated temperatures without charring, discoloring, or becoming brittie, and have good dielectric properties and high mechanical strength.

The following examples illustrate certain embodiments of the inventionbut are not to be construed as limiting the same:

10 pounds of aspen wood, in the form of sawdust, was treated for 5 hoursat C. under autogenous pressure with a liquor consisting of 133 poundsof water, '7 pounds of sodium hydroxide, and 16 pounds of sodiumphenate, to form a dispersion of cellulose fibers in an aqueous solutionof phenolate-lignin complex. The suspended cellulose represented 40 percent of the original weight of the wood. The reaction mixture was thencooled to 40 C. and adjusted to a pH of 9.5 by addition of hydrochloricacid. 28 pounds of 40 per cent formaldehyde solution was thereaftermixed with the partially acidified reaction product and the mixtureheated at 107 C. for 20 minutes to condense the formaldehyde with thephenolate complex present in the digestion product. The resultingwater-soluble condensation product was precipitated upon the suspendedcellulose fibers by cooling the reaction mass to 30 C. and addinghydrochloric acid with agitation until a pH of 5 was attained. Thefilled resinous product was filtered off, washed, airdried, and ground.The flow characteristics of this product according'to the methoddescribed by Peakes in Plastic Products 10, pages 93 and 132(1934), are0.5 inch at 500 pounds per square inch and 150 C. in 35 seconds. Testpieces of dimensions were molded from the resin at 2000 pounds persquare inch at 150 C. The molded samples were tested for acid resistanceby determining their loss in weight after boiling in 40 per centsulfuric acid for 6 hours and in. 10 per cent sulfuric acid for 24hours, respectively. In both series of experiments an average loss inweight of 3 per cent was observed. Other samples were tested forresistance to boiling water, and showed an average loss in weight of 2per cent after refluxing for 24 hours in this medium. The surfaces ofthe test samples were not appreciably affected by such treatment. Atelevated tem- A filled resin was made from 10 pounds of aspen wood underthe conditions described in the above example with the exception thatcondensation with formaldehyde was carried out at 95 C. for 20 minutes.The washed and dried resin was ground in a planetary disc mill and 70parts by weight of it were mixed with 30 parts by'weight of wood flourin a ball mill to make a molding powder which molded satisfactorilyunder conditions similar to those used in Example 1.

Example 3 A hardwood distillate oil comprising 50-70 per cent by weightof monoand polyhydric phenols and alkylated and ether derivativesthereof was extracted with dilute sodium hydroxide solution. A quantityof this distillate was mixed with sodium phenolate solution to form 56.4pounds of solution containing the sodium salts of 6.75 pounds of phenoland 0.75 pound of phenolic derivatives from the hardwood distillate.Sufficient sodium hydroxide was added to this mixture to give a causticconcentration of 7.9 per cent. This solution was treated with pounds ofaspen hog chips under autogenous pressure at 180 C. for 4 hours. Thepartially-digested mixture was thereafter treated as described inExample 1 with the exception that only 13.3 pounds of 40 per centformaldehyde was used in the condensation step. The resulting filledresin molded readily at 150 C. under 500 pounds per square inch pressureand showed a fiow characteristic of 1.22 inches. Under these conditionsof temperature and pressure, the resin test pellet set to a hard,infusible mass in 35 seconds.

We claim:

1. A process for the preparation of a thermosetting resin compositionwhich comprises the steps of pulping a ligno-cellulosic material underalkaline conditions and below the decomposition temperature of themixture with a hot aqueous liquor comprising alkali and a water-solublephenolate of the group consisting of the alkali metal, alkaline earthmetal, and ammonium phenolates as active pulping agents to form asuspension of cellulosic fibers in a solution comprising aphenolate-lignin complex, cooling, adding an aldehyde to the reactionmixture, heating the mixture for a sufiicient time to cause reaction ofthe aldehyde with the phenolate complex but insufficient to causeprecipitation, and acidifying the mixture to precipitate athermo-setting resin product upon the suspended fibers.

2. A process for the preparation of a thermosetting resin compositionwhich comprises the steps of pulping a ligno-cellulosic material underalkaline conditions and below the decomposition temperature of themixture with a hot aqueous liquor comprising alkali and a water-solublephenolate of the group consisting of the alkali metal, alkaline earthmetal, and ammonium phenolate as active pulping agents to form asuspension of cellulosic fibers in a solution comprising aphenolate-lignin complex, cooling, adding an aldehyde to the reactionmixture, heating the mixture at a temperature below 150 C. for asufficient time to cause reaction of the aldehyde with the phenolatecomplex but insufficient to cause precipitation, acidifying the mixtureto precipitate a thermo-setting resin product upon v the suspendedfibers, andseparating and drying the precipitate.

, 3. A process for the preparation of a thermosetting resin compositionwhich comprises the steps of pulping a ligno-cellulosic material underalkaline conditions and below the decomposition temperature of themixture with a hot aqueous liquor comprising alkali and a water-solublephenolate of the group consisting'of the alkali metal, alkaline earthmetal, and ammonium phenolates as active pulping agents to form asuspension of cellulosic fibers in a solution comprising aDhenolate-lignin complex, cooling, adding an aldehyde to the reactionmixture, heating the mixture at a temperature below C. for a suflicienttime to cause reaction of the aldehyde with the phenolate complex butinsufficient tocause precipitation, adding a filler, acidifying themixture to precipitate a thermo-setting resin product upon the suspendedsolids, and separating and drying the precipitate.

4. A process for the preparation of a thermoset molding which comprisesthe steps of pulping a ligno-cellulosic material under alkalineconditions and below the decomposition temperature of the mixture with ahot aqueous liquor comprising alkali and a water-soluble phenolate ofthe group consisting of the alkali metal, alkaline earth metal, andammonium phenolates as active pulping agents to form a suspension ofcellulosic fibers in a solution comprising a phenolate-lignin complex,cooling, adding an aldehyde to the reaction mixture, heating the mixtureat a temperature below 150 C. for a sufiicient time to cause reaction ofthe aldehyde with the phenolate complex but insufficient to causeprecipitation, acidifying the mixture to precipitate a thermo-settingresin product upon the suspended fibers, and separating and drying theprecipitate and molding the same by subjecting said material to heat andpressure.

5. A process for the preparation of a thermosetting resin compositionwhich comprises the steps of pulping a ligno-cellulosic material at150-180 C. under alkaline conditions and autogenous pressure withaqueous liquor comprising alkali and a'water-soluble phenolate of thegroup consisting of the alkali metal, alkaline earth metal, and ammoniumphenolates as active pulping agents to form a suspension of cellulosicfibers in a solution comprising a phenolate-lignin complex, cooling,adding an aldehyde to the reaction 150-180 C. under autogenous pressurewith an,

aqueous liquor comprising alkali and a watersoluble phenolate of thegroup consisting of the alkali metal, alkaline earth metal, and ammoniumphenolates in relativeamounts such that the ratio of the pound-moles ofalkali and of phenolate to pounds ofligno-cellulosic material in thedigestion mixture both lie between the limits 0.005 and 0.02, cooling,adding an aldehyde to the reaction mixture, heating the mixture at asetting resin composition which comprises the steps of pulping a.ligno-cellulosic material at 150-180 C. with an aqueous liquorcomprising sodium hydroxide and water-soluble phenolate of the groupconsisting of the alkali metal, alkaline earth metal, and ammoniumphenolates in relative amounts such that the ratio the pound-moles ofsodium hydroxide and of phenolate to po'unds'oi ligno-cellulosicmaterial in the digestion mixture both lie between the limits 0.005 and0.02, cooling, partially neutralizing the excess alkali, adding analdehyde to the reaction mixture, heating the mixture at a temperaturebelow 150 C. for suflicient time to cause reaction 01. the aldehyde withthe phenolate complex but insuflicient to cause precipitation,acidifying the mixture to precipitate a thermo-setting resin productupon the suspended fibers, and separating and drying the precipitate.

8. A process for the preparation of a thermosetting resin compositionwhich comprises the steps of pulping a ligno-cellulosic material at150-180 C. with an aqueous liquor comprising sodium hydroxide andwater-soluble phenolate of the group consisting of the alkali metal,alkaline earth metal, and ammonium phenolates in relative amounts suchthat the ratio of the pound-moles of sodium hydroxide and of phenolateto pounds of ligno-cellulosic material in the digestion mixture both liebetween the limits 0.005 and 0.02, cooling, partially neutralizing theexcess sodium hydroxide to a pH of between 9 and 10, adding an aldehydeto the reaction mixture, heating the mixture at a temperature below 150-C. for sufilcient time to cause reaction of the aldehyde with thephenolate complex but insufiicient to cause precipitation, acidifyingthe mixture to precipitate a thermo-setting resin product upon thesuspended fibers, and separating and drying the precipitate.

9. A process for the preparation of a thermosetting resin compositionwhich comprises the steps of pulping a ligno-cellulosic material at150-180 C. with an aqueous liquor comprising sodium hydroxide and sodiumphenolate in relative amounts such that the ratio of the poundmoles ofsodium hydroxide and of phenolate to pounds of ligno-cellulosic materialin the digestion mixture both lie between the limits 0.005

tion mixture both lie between the limits 0.005 and and 0.02, cooling,partially neutralizing the excess alkali to a pH of between 9 and 10,adding an aldehyde in amount sufiiclent to provide a molar ratio ofaldehyde to phenol present cl. from 2.0 to 2.5, heating the mixture'at atemperature below 150 C. for sullicient time to cause reaction of thealdehyde with the phenolate complex but insuiiilcient to causeprecipitation, acidifying the mixture to precipitate a thermo-settingresin product upon the suspended fibers, and separating and drying theprecipitate.

10. A process for the preparation of a thermosetting resin compositionwhich comprises the steps of pulping a ligno-cellulosic material at150-180 C. with an aqueous liquor comprising sodium hydroxide and sodiumphenolate in relative amounts such that the ratio of the poundmoles ofsodium hydroxide and of phenolate to pounds of llgno-cellulosic materialin the diges- 0.02, partially neutralizing the excess alkali to a pH ofbetween 9 and 10, cooling, adding an aldehyde in amount suflicient toprovide a molar ratio of aldehyde to phenol present of from 2.0 to 2.5,heating at a temperature of from to C. for sufficient time to causereaction of the aldehyde with the phenolate complex but insuflicient tocause precipitation, acidifying the mixture to precipitate athermo-settin'g resin prodnot upon the suspended fibers, and separatingand drying the precipitate.

11. A process for the preparation of a thermosetting resin compositionwhich comprises the steps of pulping a ligno-cellulosic material at -180C. with an aqueous liquor comprising sodium hydroxide and sodiumphenolate in relative amounts such that the ratio of the poundmoles ofsodium hydroxide and of phenolate to pounds of ligno-cellulosic materialin the digestion mixture both lie between the limits 0.005 and 0.02,partially neutralizing the excess alkali to a pH of between 9 and 10,cooling, adding an aldehyde in amount suflicient to provide a molarratio of aldehyde to phenol present of from 2.0 to 2.5, heating at atemperature of from 90 to 110 C. for suflicient time to cause reactionof the aldehyde with the phenolate complex but insufiicient to causeprecipitation, adding filler, acidifying the mixture to precipitate athermosetting resin product upon the suspended solids, an? separatingand drying the filled resin produc WILLIAM R. COLLINGS. RICHARD D.FREEMAN. RICHARD M. UPRIGHT.

